1. Field of the Invention
This invention relates to cloth spreading machines, and more particularly to cloth spreading machines of the type which move reciprocably longitudinally over a cloth spreading table and spread layers of cloth upon the table.
2. Prior Art
Reciprocating cloth spreaders are well known in the art, having been in use for many years. The U.S. patents to Martin, et al. (U.S. Pat. No. 3,479,023) and Benson, et al. (U.S. Pat. No. 3,684,273) illustrate the general features of this type of machine. In laying or spreading cloth from a roll, the ideal situation is to put down a layer of cloth which is straight, smooth (flat) and tension free so that material usage is maximized.
Tension exists in a roll of cloth due to the manner in which the cloth is rolled up at the textile mill. Certain prior art workers have directed their efforts toward producing a tension free lay of cloth; the U.S. patents to Benson, et al. (U.S. Pat. No. 3,684,273) and Frederick, et al. (U.S. Pat. No. 3,782,649) underscore this fact. However, solutions proposed to date have been largely unsatisfactory. The mechanisms devised generally sense the tension of the web of cloth as it is being unrolled and spread; an appropriate adjustment is made in the speed of the cloth removal according to the conditions sensed. The problem lies in that these devices generally operate on an "on-off" system so that the response to overfeeding or underfeeding is abrupt and jerky. Although efforts have been made to smooth out this movement, as in U.S. patent to Benson, et al. (U.S. Pat. No. 3,684,273), for example, the prior art does not disclose a truly effective means for eliminating the tension.
Another problem rests in producing a lay of cloth with a straight edge, so that as layers of cloth are built up on the spreading table, the edges of the web will property align and waste of material will be minimized. Various factors contribute to this problem, including tight or loose selvage in the material that produces an arc or curve in the web of cloth and a tapered roll of cloth that results from improper winding at the mill. In an attempt to control these variables, machines typically incorporate some type of steering mechanism to act in conjunction with an edge position sensor, such as a photo-electric eye, and adjust the position of the roll accordingly as shown in U.S. patent to Martin, et al. (U.S. Pat. No. 3,479,023). However, these devices fall short of the desired result. Typically, the position of the cloth is adjusted a significant distance from the point at which the cloth meets the table; this distance may allow the cloth to move out of alignment before it reaches the table. In addition, the prior art devices generally move the roll by moving the rod which carries the roll of material. For large rolls of slick material, silk for example, the center of the roll may move, but the material coming off the roll slips over the underlying cloth and remains out of alignment.
Prior art devices are also unsatisfactory in the manner in which large rolls of cloth are loaded onto and driven by the cloth spreading machine. If the entire weight of the roll of cloth rests on a single driver, the cloth tends to tear or deform and be improperly fed. Prior art devices have attempted to control the weight against any one driver by using multiple drivers or providing partial overhead support for the weight of the large roll. However, these methods greatly increase the complexity and related cost of manufacture of cloth spreading machine.